The present invention relates to an electronic part including as an active device a semiconductor crystal layer formed by epitaxial growth on a seed crystal substrate, and a method of producing the same. Furthermore, the present invention relates to an image display system including such electronic parts, and a method of manufacturing the same.
In the case of arranging light-emitting devices in a matrix form to assemble an image display system, it has hitherto been practiced to forming the devices directly on a substrate such as in the cases of a liquid crystal display system (LCD) and a plasma display panel (PDP) or to arrange singular LED packages in the case of a light-emitting diode display (LED). For example, in the cases of the image display systems such as LCD and PDP, the devices cannot be separated individually, so that it has been a usual practice to form the devices spaced from each other by the pixel pitch of the image display system, from the beginning of the manufacture process.
On the other hand, in the case of the LED display, it has been practiced to take out the LED chips after dicing, and connect the LED chips individually to external electrodes by bump connection using wire bonding or flip chips, thereby packaging the LED chips. In this case, the LED chips are arranged at the pixel pitch of the image display system before or after the packaging, and the pixel pitch is made to be independent from the pitch at which the devices are produced.
Since the LED (Light-Emitting Diode) as the light-emitting device is expensive, it is possible to lower the cost of the image display system using the LEDs by producing a multiplicity of LED chips from a single sheet of wafer. Namely, where the size of the LED chips is several tens of xcexcm square, as contrasted to about 300 xcexcm square in the related art, and the LED chips are connected to manufacture an image display system, it is possible to reduce the price of the image display system.
Meanwhile, among the individual semiconductor devices such as not only the light-emitting diode but also, for example, laser diode and transistor device, there are some devices in which the overall area of the device must be not less than several times of the active region (for example, not less than 0.2 mm square) although the size of the active region necessary for operation is on the order of xcexcm. This hampers an enhancement of the actual mounting density of the device or a lowering in the cost of the device.
For example, in the case of high-luminance LED, in account of the fact that a luminance of about several cd is obtained at a chip size of about 300 xcexcm square and according to proportional shrinkage, low-luminance LED with a luminance of not more than about several mcd might have an active region (active layer area) of about 10 xcexcm square. However, according to the conventional device structure and conventional mounting method, it is difficult to set the overall size of the device closer to the size of the active region. In the case of laser diode, the active region is in a stripe form with a width of several xcexcm and a length of several hundreds of xcexcm, but in actual mounting, the device size has a width of not less than about 200 xcexcm.
Particularly, in the case of a light-emitting diode or a laser diode that is produced by epitaxial growth of a gallium nitride based crystal on a sapphire substrate, the cathode side (n-type semiconductor layer) and the anode side (p-type semiconductor layer) are sequentially laminated. In this case, since the substrate is an insulating body, two electrodes must be provided on the growth surface side, so that the device size is large due to wire bonding, but the actual area of the active region (active layer) is rather small. Therefore, internal resistance is high due to flow of current in a lateral direction, and several drawbacks such as unfavorable concentration of current are generated.
On the other hand, in the case of a light-emitting diode composed of an aluminum gallium indium phosphide based crystal grown on a gallium arsenide substrate, electrodes can be provided on both sides of the device, but a portion of the light emitted at an active layer is absorbed by the substrate, so that only an external light emission efficiency much lower than an intrinsic internal light emission efficiency can be obtained. In order to solve this problem, a variety of contrivances have been practiced, for example, formation of a semiconductor multilayer film (DBR) for light reflection in the inside, formation of a thick window layer, or a transfer onto a transparent substrate. These contrivances lead to a rise in cost.
The present invention has been proposed in consideration of the above situations in the related art. Accordingly, it is an object of the present invention to provide an electronic part in which the number of devices formed from a single sheet of crystalline wafer can be enlarged as compared with the conventional packaged devices, production cost can be reduced, and it is easy to mount the electronic part in high density, and a method of producing the same. In addition, it is another object of the present invention to provide a large-type system, a high-performance system, and a system based on integration of a different kinds of devices (for example, image display system), which cannot be realized with a system based on integration of a multiplicity of devices produced by a monolithic process.
In order to attain the above objects, according to an aspect of the present invention, there is provided an electronic part, semiconductor crystal layer formed by epitxial growth on a seed crystal substrate is embedded in an insulating material in the condition where the seed crystal substrate is removed, electrodes are provided on a first surface of the semiconductor crystal layer and a second surface of the semiconductor crystal layer opposite to the first surface, and lead-out electrodes connected to the electrodes are led out to the same surface side of the insulating material. A method of producing an electronic part according to the present invention includes a step of epitaxial growth of a semiconductor crystal layer on a seed crystal substrate, a step of embedding the semiconductor crystal layer in an insulating material and removing the seed crystal substrate, a step of forming an electrode connected to one surface of the semiconductor crystal layer, a step of transferring the semiconductor crystal layer embedded in the insulating material onto a support substrate, a step of forming an electrode connected to the opposite side surface of the semiconductor crystal layer, and a step of forming lead-out electrodes connected to the electrodes by leading out the lead-out electrodes to the same surface side of the insulating material.
In the electronic part having the above-mentioned structure, the region necessary for actual mounting and leading-out of electrodes is minimized, and the overall size of the device is suppressed to be small. In addition, for example, in the case of a light-emitting diode, a laser diode, or the like produced by epitaxial growth of a gallium nitride based crystal on a sapphire substrate, such problems as an increase in internal resistance and unfavorable concentration of current are dissolved. In the case of a light-emitting diode including an aluminum gallium indium phosphide based crystal grown on a gallium arsenide substrate, high light emission efficiency is realized, and such contrivances that may cause a rise in cost are unnecessary.
On the other hand, according to another aspect of the present invention, there is provided an image display system including electronic parts including light-emitting devices arranged in a matrix form on a substrate, each of the electronic parts constituting a pixel. A semiconductor crystal layer functioning as a light-emitting device produced by epitaxial growth on a seed crystal substrate is embedded in an insulating material in the condition where the seed crystal substrate is removed, electrodes are provided respectively on a first surface of the semiconductor crystal layer and a second surface of the semiconductor crystal layer opposite to the first surface, each of the electronic parts is covered with an insulating layer, and lead-out electrodes each connected to each of the electrodes of the semiconductor crystal layer contained in the electronic part are led out to the face side of the insulating layer. In addition, a method of manufacturing an image display system according to the present invention resides in a method of manufacturing an image display system including electronic parts including light-emitting devices arranged in a matrix form on a substrate, each of the electronic parts constituting a pixel. The method includes a step of epitaxially growing semiconductor crystal layers for functioning as light-emitting devices on a seed crystal substrate, a first transfer step of transferring the semiconductor crystal layers onto a first temporary holding member in the condition where the semiconductor crystal layers are spaced wider apart than they have been arranged on the seed crystal substrate and holding the semiconductor crystal layers by embedding the semiconductor crystal layers in an insulating material, a step of forming electrodes connected to one side of the semiconductor crystal layers, a second transfer step of transferring the semiconductor crystal layers embedded in the insulating material onto a second temporary holding member, a step of forming electrodes connected to the opposite side of the semiconductor crystal layers, a step of cutting the insulating material with the semiconductor crystal layers embedded therein to separate individual electronic parts, a third transfer step of transferring the electronic parts held on the second temporary holding member onto a second substrate while spacing the electronic parts further wider apart, a step of providing an insulating layer so as to cover each of the electronic parts, and a step of leading out, to the face side of the insulating layer, lead-out electrodes connected to the electrodes of the semiconductor crystal layers contained in the electronic parts.
According to the image display system and the method of manufacturing the same, the light-emitting devices rearranged in the spaced-apart condition are arranged in a matrix form to constitute an image display portion. Therefore, the light-emitting devices produced by fine processing with a dense condition, namely, with a high degree of integration can be efficiently rearranged in the spaced-apart condition, and productivity is largely enhanced. In addition, the light-emitting devices converted into electronic parts can be actually mounted in a high density, and wiring therefor can be easily formed.
According to the present invention, it is possible to provide an electronic part such that the number of devices produced from a single sheet of crystal wafer can be enlarged as compared with the conventional packaged devices, the production cost can be reduced, and actual mounting in a high density is easy. In addition, it is possible to provide a large-type system, a high-performance system, and a system based on integration of different kinds of devices (for example, an image display system), which cannot be realized with a system based on integration of a multiplicity of devices produced by a monolithic process. On the other hand, according to the image display system and the method of manufacturing the same according to the present invention, while the above-mentioned merits are maintained, the light-emitting devices produced by fine processing with a dense condition, namely, with a high degree of integration can be efficiently rearranged with the spaced-apart condition. Therefore, an image display system with high accuracy can be produced with high productivity.